Viewport output on videocard
we have several builds that recover BGE/UPBGE for Blender 2.8.
UPBGE has the possibility to input/output to a decklink card.

In this link (https://mega.nz/#F!t9EEFSaS!JPiOPSInCZyU-SW_-rhEOQ) builds from 2019/11/04 have decklink activate: 

Maybe we need to update decklink examples (as in https://docs.blender.org/api/blender_python_api_2_78b_release/bge.texture.html) to use new Opengl shader version. We are in process.